What good is half a wing?

The question "what good is half a wing" is often used by creationists who severely misunderstand evolutionary theory. The question relates to the idea that fossil birds should be discovered with literal "half-wings", i.e. a wing missing half of itself. This is a misunderstanding of how wings evolve. Evolution has no goal, so it's not working towards a full-blown modern wing like we know them today. All it's doing is working towards something that helps the organism in some way. For example, a dinosaur's arm could grow small proto-feathers in order to help it stay in the air longer when it jumps. This isn't a wing yet, but it is beneficial. Over the millenia, the feathers grow, the arms and muscles change, and by modern times we do have wings as we know them.